1. Field of the Invention
The present invention relates to a high pressure fuel injection pipe for a diesel engine having a small tubular diameter of approximately not more than 30 mm which is arranged in the vicinity of a diesel engine as a fuel supply passage specially in the field of a diesel engine, and more particularly to a high pressure fuel injection pipe for a diesel engine which is characterized by its connection structure with a counterpart member such as a nozzle holder.
2. Related Art Statement
As shown in FIG. 10 as an example, a nozzle holder side of a high pressure fuel injection pipe for a diesel engine is constituted such that an injection pipe body 21 is provided with a connecting head 21-1 at an end portion thereof and a fastening nut (generally called xe2x80x9chole boltxe2x80x9d) 23 is assembled to the injection pipe body 21 by way of a press member 22 such as a washer which is disposed behind the connecting head 21-1, and a press seat portion 21-Ia formed on the connecting head 21-1 of the injection pipe body 21 is brought into contact with and is engaged with a pressure receiving seat portion 24a of a nozzle holder 24, and the injection pipe body 21 is connected to the nozzle. holder 24 by fastening with a pressing force applied to the connecting head 21-1 due to the threaded engagement of the fastening nut 23 with the nozzle holder 24. In FIG. 10, numeral 25 indicates a seal member and numeral 26 indicates a head cover of an engine.
However, the above-mentioned press member 22 is not always required to be provided. Therefore, the fuel injection pipe can be formed without provision of the press member, wherein a neck part below the connecting head 21-1 is directly fastened by the fastening nut 23 to connect with the nozzle holder 24.
In such a conventional high pressure fuel injection pipe, however, when fuel leaks into the inside of the fastening nut 23 due to flaws present on a seat face defined between the press seat portion 21-1a of the connecting head 21-1 of the injection pipe body 21 and the pressure receiving seat portion 24a of the nozzle holder 24 or the shortage of the fastening torque of the fastening nut 23 or the failure to fasten the fastening nut 23, the leaked fuel is leaked out into the inside of the head cover 26 through the threaded engagement portion between the fastening nut 23 and the nozzle holder 24. Accordingly, there have been problems that an engine oil is diluted (dilution) thus degrading the quality of the oil and simultaneously the oil level is elevated thus producing a white fume in an exhaust gas and increasing toxic substances in the exhaust gas. Further, conventionally, the leakage of the fuel through the seat face can be detected only by way of the recognition of the above-mentioned white fume so that it has been impossible to take a prompt countermeasure against the leakage of the fuel.
The present invention has been made in view of the above-mentioned drawbacks of the prior art and it is an object of the present invention to provide a high pressure fuel injection pipe for a diesel engine which is capable of detecting the leakage of fuel from a seat portion such that in case the fuel is leaked from a seat face defined between a press seat surface of a connecting head of an injection pipe body and a pressure receiving seat portion of a counterpart member such as a nozzle holder by a chance, the leaked fuel is led to the outside of a head cover.
The first aspect of the present invention is directed to a high pressure fuel injection pipe for a diesel engine which is constituted such that an injection pipe body is provided with a connecting head at an end portion thereof and a fastening nut is assembled to the injection pipe body by way of a press member which is disposed behind the connecting head, and a press seat portion formed on the connecting head of the injection pipe body is brought into contact with and is engaged with a pressure receiving seat portion of a nozzle holder which works as a counterpart member, and the injection pipe body is connected to the nozzle holder by fastening with a pressing force applied to the connecting head due to the threaded engagement of the fastening nut with the nozzle holder, wherein the improvement is characterized by being constituted such that an annular washer provided with at least one recessed groove or one small hole which extends in the radial direction on a circumference thereof is used as the press member which is interposed between the connecting head of the injection pipe body and the fastening nut, and fuel leaked into the inside of the fastening nut from a seat portion defined between the press seat portion formed on the connecting head and the pressure receiving seat portion of the counterpart member is led to the outside through the recessed groove or the small hole of the washer.
The second aspect of the present invention is directed to a high pressure fuel injection pipe for a diesel engine which is constituted such that an injection pipe body is provided with a connecting head at an end portion thereof and a fastening nut is assembled to the injection pipe body by way of a press member which is disposed behind the connecting head, and a press seat portion formed on the connecting head of the injection pipe body is brought into contact with and is engaged with a pressure receiving seat portion of a nozzle holder which works as a counterpart member, and the injection pipe body is connected to the nozzle holder by fastening with a pressing force applied to the connecting head due to the threaded engagement of the fastening nut with the nozzle holder, wherein the improvement is characterized by being constituted such that a through hole or a radially extending groove for leading fuel leaked into the inside of the fastening nut from a seat portion defined between the press seat portion formed on the connecting head and the pressure receiving seat portion of the counterpart member to the outside is formed in the fastening nut in the vicinity of the press member.
The third aspect of the present invention is directed to a high pressure fuel injection pipe for a diesel engine, which is constructed such that a press seat portion formed on the connecting head of the injection pipe body is brought into contact with and is engaged with a pressure receiving seat port of a nozzle holder and is fastened with a pressing force applied to the connecting head due to the threaded engagement of the fastening nut so as to connect the nozzle holder to the connecting head, wherein a through hole is formed in the vicinity of the connecting head of the fastening nut, the through hole of which being to discharge to the outside a fuel leaked into the fastening nut from the pressure receiving seat and the pressure receiving set portion of the nozzle holder.
Further, in the present invention, if necessary, a seal member may be disposed in the vicinity of an outer end portion of a threaded engagement portion defined between the fastening nut and the nozzle holder.
In the high pressure fuel injection pipe for a diesel engine according to the present invention, the annular washer having the radially extending groove or small hole is used as the press member interposed between the connecting head of the injection pipe body and the fastening nut, or the through hole is formed in the fastening nut per se, and the seal member is preferably disposed in the vicinity of the outer end portion of the threaded engagement portion defined between the fastening nut and the nozzle holder. Accordingly, the leakage of the fuel leaked from the seat face defined between the press seat portion of the connecting head of the injection pipe body and the pressure receiving seat portion of the nozzle holder into the inside of the head cover can be prevented and simultaneously the leaked fuel can be led to the outside of the head cover so that the leakage of the fuel caused by the abnormal condition of the seat face, the shortage of the fastening torque of the fastening nut or the failure to fasten the fastening bolt can be instantly detected in a trial operation after assembling an engine whereby the countermeasure against the leakage of the fuel can be taken promptly.